1. Field of the Invention
This invention relates to new moldable, radically polymerizable multicomponent mixtures which are used, for example, as free-flowing or spreadable compositions or as pastes and then hardened under ambient conditions through initiation of the polymerization reaction. In applicational terms, the invention relates in this regard to almost any field where radically polymerizable or curable compositions are used, including for example adhesives, sealing compounds, the specific production of plastics moldings, surface coating with air-hardening and, in particular, solventless paint systems and the like.
2. Discussion of Related Art
The peroxide- or hydroperoxide-initiated hardening of olefinically unsaturated systems requires activator systems made up of several components, particularly when the reaction is to be initiated at low temperatures, for example at room temperature or only slightly elevated temperature. It is known that selected tertiary amine compounds partly aromatically substituted at the nitrogen atom perform such an activating function. Known activators for the initiation of polymerization reactions by benzoyl peroxide, for example, are in particular dimethyl aniline and dimethyl-p-toluidine.
A totally different known class of activators for oxidative initiation of the polymerization of certain unsaturated systems, namely drying oils, are metal compounds--at least partly soluble in the system--of metals which can occur in several valency stages and accelerate the initiating reaction through intermediate shifts in valency on interaction with other components of the system. Metal compounds such as these--sufficiently soluble in organic solvents and/or in binders--of metals of the type in question have long been known as so-called driers for the air drying of paints, varnishes and the like based on unsaturated oils. Sufficiently oil-soluble compounds of transition metals, which are capable of occurring in several valency stages, are particularly suitable for this purpose. The individual components differ in their ability to accelerate hardening, compounds of cobalt and/or manganese being particularly suitable, although iron also accelerates hardening. In addition to and, in particular, in combination with these highly active metallic components, it is possible to use comparable compounds of other metals which may also be capable of forming several valency stages. A detailed description of such systems can be found, for example, in "Ullmann, Encyklopadie der technischen Chemie", 4th Edition, Vol. 23 (1983), 421-424.
It is also known that the two types of promoters described here for the radical initiation of polymerization can lead by interaction to an enhanced effect. For example, the Article by L. HORNER et al "Autoxidationsstudien an N,N-dialkylierten Anilinderivaten (Autoxidation Studies on N,N-Dialkylated Aniline Derivatives", in Makromolekulare Chemie 93 (1966), 69 to 108, relates to investigations into the acceleration of the spontaneous autoxidation of N-dialkyl-substituted arylamine compounds in pure, highly dry oxygen gas. In the first stage of the spontaneous autoxidation, the amine hydroperoxide compound is formed at aliphatic CH groups in the .alpha.-position under the effect of dried, superpure oxygen. This spontaneous autoxidation of the N,N-dialkylated arylamines takes place very slowly. According to the Article in question, the co-use of cobalt(II) compounds and, to a lesser extent, the co-use of iron(III) salts results in activation of the autoxidation process. In further studies reported in this Article, it is shown that acetic acid also has a pronounced accelerating effect on autoxidation at the teriary amine compound whereas stronger acids, such as trichloroacetic acid, or mineral acids form true tertiary ammonium salts which are not autoxidizable. The use of cobalt ions in conjunction with acetic acid leads to the vigorously catalyzed autoxidation of dialkyl aniline compounds under the effect of superpure oxygen.
Finally, the Article cited above describes studies into the initiation of the polymerization of vinyl compounds by the dimethyl aniline/superpure oxygen/cobalt salt system. High-purity acrylonitrile, methyl methacrylate, ethyl acrylate and styrene can be polymerized with this system. The initiating reaction is interpreted as redox catalysis in which molecular oxygen acts as oxidizing agent. There are no references in the publication in question to the suitability of the multicomponent systems investigated for practical use in the polymerization field. In fact, however, these theoretical works, which have been available to experts for almost 25 years, have not provided any encouragement for their practical application.
The problem addressed by the invention is to utilize existing knowledge of multicomponent redox systems as described above in developing new possibilities for the practical application of activator systems which may be used in simplified manner for initiating the polymerization of olefinically unsaturated systems. The activator systems are intended to be able, in admixture with radically polymerizable materials or mixtures, to be activated by contact with ambient air. In preferred embodiments, this activation is intended to take place at temperatures as low as room temperature, although a moderate increase in temperature may be applied. In one particularly important embodiment, the invention relates to multicomponent mixtures of the type mentioned which are capable, simply by contact with ambient air at room temperature, of initiating the starting reaction of a radical polymerization of unsaturated systems with time-controlled hardening and a predeterminable pot life.